The United Nations marked World Food Day on Wednesday, warning against food waste as 842 million people go hungry each year. They also stressed the importance of healthy diets amid rising obesity. Around a third of food produced globally currently goes to waste -- some 1.3 billion tonnes a year, according to the Rome-based UN Food and Agriculture Organisation. "With just a quarter of that, we could feed the 842 million hungry," said Robert van Otterdijk, an agriculture industry expert at FAO. Halving the amount of food wasted would mean only needing to raise world food production by 32 per cent to feed the world's population in 2050, instead of the 60 per cent currently estimated. Mathilde Iweins, coordinator of a report on the cost of food waste, said that "the agricultural areas used to produce the food that will never be eaten are as big as Canada and India combined". But the FAO said focusing on the type of food being consumed was just as important, warning that malnutrition and poorly-balanced diets impose high costs on society -- from towering health care bills to lost productivity. Over 165 million children are so malnourished they will never reach their full physical and cognitive potential. About two billion people in the world lack vitamins and minerals that are essential for good health while 1.4 billion people are overweight. The FAO said it was particularly excited by projects aimed at raising the micronutrient content of staple foods -- either through 'biofortification' or by encouraging the use of varieties with higher nutrient content.